[En-Nut-Discussion] Major memory mapping changes?

[Carlos]

Hi all,

Radek, I had a similar problem and after taking a look at the ethernut 2.0
schematics I have seen what Pavel and Harald told:

1.- "One difference between Ethernut 1 and 2 is the voltage level. Ethernut
1 uses a 5V 74HC to latch the upper address bits while Ethernut 2 uses the
3.3V CPLD"
2.- "There _must_ be a latch to obtain 16-bit wide address bus, as on the
MCU side the data lines and half of address lines share the same pins."

So, if I am not wrong, in the Ethernut 2.0 board expansion port, lines
ranging from A0 to A7 work at 3.3V (because they are latched in the 3.3V
CPLD), and lines A8 to A15 work at 5V, because they are connected directly
to the MCU.

Could anyone confirm this, please?

Many thanks in advance,
Carlos.

-----Mensaje original-----
De: en-nut-discussion-bounces at egnite.de
[mailto:en-nut-discussion-bounces at egnite.de] En nombre de Radek Podgorny
Enviado el: lunes, 08 de noviembre de 2004 15:41
Para: Ethernut User Chat (English)
Asunto: Re: [En-Nut-Discussion] Major memory mapping changes?

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Hi everybody,

so I'm back with my problem. We've been working hard trying to resolve the
bug and after a time, even the 1.3 started to make errors so it's NOT
ethernut related. We're currently reworking our external circuitry so I'll
let you know in few days...

Thanks for the effort though...
Radek

>
>
> Hello Radek,
>
> Radek Podgorny wrote:
>
>> I thought the address and data bus is connected directly to the MCU.
>
> There _must_ be a latch to obtain 16-bit wide address bus, as on the 
> MCU side the data lines and half of address lines share the same pins.
> Have a look into datasheet, search for ALE signal.
>
>> So
>> there is a latch somewhere in between operating at 3.3V? If you're 
>> talking about the CPLD itself, the 3.3V level it outputs shouldn't 
>> matter as long as the levels on the "main" bus (the one connected 
>> directly to the MCU and the pins) is 5V.
>
> Not necessarily, I belive that CPLD is 5V tolerant and even 3.3V 
> singals reach the MCU theshold.
>
> Pavel
> _______________________________________________
> En-Nut-Discussion mailing list
> En-Nut-Discussion at egnite.de
> http://www.egnite.de/mailman/listinfo.cgi/en-nut-discussion
>


-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.2.6 (GNU/Linux)

iD8DBQFBj4Ve7mej6pjlbYQRAh6+AJ9gIMN40b/a60SDuhJV/VppSdGtugCdFByp
VSoQUy53MJChKvCQsO2XtWE=
=n3Rt
-----END PGP SIGNATURE-----

_______________________________________________
En-Nut-Discussion mailing list
En-Nut-Discussion at egnite.de
http://www.egnite.de/mailman/listinfo.cgi/en-nut-discussion